Field of the Invention and Prior Art
The invention relates to high-density foam and is particularly directed to rigid polyurethane and isocyanurate-modified polyurethane foam having a density of at least 20 pounds per cubic foot.
Rigid polyurethane and isocyanurate-modified polyurethane foams have been variously described in literature, both in patent and scientific papers by various authors. Almost all of these isocyanate-based foams containing various fillers were primarily produced by two methods, and almost all of them were intended for insulation purposes. See, for example U.S. Pat. Nos. 3,382,302; 4,163,824; and 4,283,563. They have been produced either continuously for low-density (2-3 pcf) thermal insulation (board stock) or by molding of panels. Various equipment has also been designed for that purpose.
However, very little has been disclosed in literature or patents regarding high-density, rigid polyurethane or isocyanurate-modified polyurethane foams designed for structural purposes and having strength properties comparable to wood, although a number of molding methods including reinforced reaction molding (RRIM) have been developed for the production of molded parts, especially for the automotive, furniture and appliance industries.
An object of this invention is the continuous production of high-density foams comprising special types of polyurethane and isocyanurate-modified polyurethane foams, especially in combination with various fillers and reinforcing fibers which are uniquely designed to provide a combination of mechanical strength properties, and environmental (outdoor weathering) properties which make them eminently suitable for applications where wood is normally used for strength and durability. Wood substitutes made of reinforced high-density, fiberglas-reinforced polyurethane foams have heretofore been prepared, for example, a product known as Centrite, and a number of like products described in Industrial And Engineering Chemistry, Product Research And Development, Vol. 23, No. 1, (1984) p.p. 81-85, by Klyotaho Morimoto and Toshio Suzuki and in Proceedings, SPI International Urethane Conference, Strasbourg, France, June 9-13, 1980, by F. Okagawa et al., p.p. 453-467.
It is an object, therefore, to provide such foams which have not only the advantage of many superior properties, such as much better dimensional stability and greatly improved weathering resistance as well as resistance to biological attack, but which can also be produced continuously in dimensions which are outside of any possibilities as far as wood boards are concerned (aside from the many imperfections in wood because of knots and splits) and to provide foams, the uniqueness of which lies also in the fact that while resembling wood in many respects, because of many physico-mechanical properties similar to wood, they can be used in applications where wood would not be practical or acceptable due to deterioration of the latter on aging.